Nick Rose/Daily JournalWorkers reveal federally mandated improvements to two of San Francisco International Airport’s four runways. The improvement project began May 17 and was slated to be completed in mid-September. It was finished early and both runways will be operational by noon Sunday, Aug. 10.

Two San Francisco International Airport runways closed since June for mandated safety improvement work will reopen Sunday, a month ahead of schedule, airport officials said.

Two of the four airport runways were closed to complete federally mandated safety improvements including extending the runways with buffer zones and safety blocks at the end in case a plane overshoots the runway.

Upgrades to the airport’s other two runways were completed last year.

The improvements are required to be completed at 40 airports nationwide by the end of 2015, but SFO has completed them 20 months in advance, airport officials said. The full cost of the project came to about $223 million.

When the latest runway closure began in June, it was estimated to be completed in mid-September.

Completing the project during the summer months was the fastest and safest way, according to the airport, taking advantage of good weather.

Airlines adjusted flight schedules during the closures and the airport made alterations to departure management so planes spent less time on the ground before takeoff.